In many computer systems, it is common to represent and convey information to a user through digital images. These images may take a variety of forms such as alphanumeric characters, graphics and other pictorial representations. The digital images may be conveyed to a user on a raster or continuous tone display device, such as a video monitor, printer and the like. Typically, the digital images are stored in digital form, manipulated and then displayed.
Digital images are generally stored as a geometric description of a scene. The description can be manipulated by the user, then converted to digital raster image data for display. How a two or three dimensional object appears when it is displayed to a user depends on numerous factors including the types of light sources illuminating the object; the object's properties including color, texture and reflectance; and the object's position and orientation with respect to the light sources, the viewer and other surfaces which may reflect light on the object.
It is often desirable to present objects for display in color. In conventional display systems, color may be applied to a region by defining a single color for the entire region (a "flat" coloring), or to add realism, a plurality of colors may be employed. A transition between colors across the surface of an object is referred to as a color gradient. In. order to display a realistic image, a smooth transition between colors across painted areas is required.